The invention concerns a fuel delivery unit, for example for supplying fuel to an internal combustion engine, such as the engine of a motor vehicle.
A typical form of a fuel delivery unit for such purposes comprises an installation holder which is operable to brace the arrangement in relation to the bottom of a fuel tank, for example by means of compression springs or flexible damping elements. It has at least one reservoir with a fuel pump disposed therein, optionally a fuel filter, and a cover closure for closing a fitting opening in the fuel tank into which the unit is fitted. Such a fuel delivery unit can be found for example in EP 0 203 244, EP 0 297 256 and for example DE 196 15 081.
Those fuel delivery units are intended to be so designed that they can be fitted and removed as a combined assembly comprising a reservoir or surge or swirl pot, a fuel pump, a fuel filter and the cover closure for the tank fitting opening, and in addition can be securely fixed on the bottom of the fuel tank. On the one hand, the aim is to ensure that the entire unit call be quickly and reliably changed in a repair or maintenance situation, while on the other hand the aim is also that such units can be adapted to any heightwise tolerances in regard to the fuel tanks used. In that respect, there have been various proposals directed at so designing the delivery unit that heightwise tolerances can be compensated by axial displaceability at least of the fuel pump, preferably the surge pot with the fuel pump disposed therein, in relation to the cover closure or a cover flange forming part of the fuel tank. For example above-mentioned EP 0 297 256 provides that the electrically powered fuel pump is designed to be axially slidable by way of a telescopic guide arrangement, with the pressure feed and return conduits, with in addition measures for supporting the fuel pump in such a way as to insulate the assembly in regard to noise.
It will be noted however that modern fuel tanks are often of such a configuration as to involve a large number of branches and other ramifications and thus afford little flat area for accommodating cover closures, cover flanges or the like, as well as also affording only limited installation volumes for fitting therein a fuel delivery unit. This means that a major demand in terms of a fuel delivery unit is for it to he as compact as possible. On the other hand however it is also necessary to ensure that the reservoir which forms part of the fuel delivery unit and which can act as a surge or swirl pot can afford an adequate volume of fuel for the fuel pump so that, even when the motor vehicle in which the tank is fitted is negotiating a bend or when the vehicle is accelerating, the engine is guaranteed a proper regular supply of fuel thereto. Finally, the volume of fuel in the reservoir often serves as a reserve of fuel. In that case, when the tank is completely emptied, the system either switches over from one or more main fuel gauges or level indicators in the fuel tank to a reserve fuel level or secondary fuel level indicator in the reservoir, in order to afford a display of maximum accuracy of the reserve amount of fuel, based on the defined volume afforded by the reservoir. The demand for the reservoir to be of the largest possible volume is however in conflict with the requirement that the fuel delivery unit is to be as compact as possible and of small dimensions so that the fitting opening for introducing the fuel delivery unit into the fuel tank in which it is to be fitted can be as small as possible. Furthermore, because of the problems in relation to sealing integrity which are related to this consideration, the fitting opening in the fuel tank should not exceed a given size.
This problem is already addressed for example in DE 32 25 929. In that arrangement the reservoir or the swirl or surge pot is made from a plurality of parts which can be secured together by a latching engagement in their position of installation on the bottom of the tank. In that case one of the parts of the swirl or surge pot forms a holder for a fuel delivery assembly which is to be subsequently inserted and which is to be installed at an angle relative to the bottom of the fuel tank in order to be able to use this arrangement even in a tank which is of relatively small structural height. However, it is not readily possible to adopt that design configuration for the reservoir in the case of a fuel delivery unit of the above-indicated kind, but rather it requires fitment of the individual parts of the reservoir and the fuel delivery assembly in a given sequence.
Reference may also be made to DE 195 28 182 disclosing a fuel delivery unit with a fuel level indicator, for installation in a fuel tank, in which a holder for accommodating a fuel delivery assembly is arranged on a tank flange in such a way as to be longitudinally slidable and rotatable. This design configuration provides that a lower end of the holder of the fuel delivery assembly can be pivotably centered on the bottom of the fuel tank or a surge or swirl pot so that an angular deviation of the flange and/or the bottom of the fuel tank from a reference position cannot have an effect on the measurement accuracy of a fuel level pick-up disposed on the fuel delivery unit. That design arrangement involves a comparatively large reservoir which accommodates the fuel pump and, with a fuel filter in a filter housing, is arranged rotatably and pivotably therewith, forming a fitting unit, by way of spring elements. Fitment of the fuel delivery unit is effected in a configuration which approximately corresponds to the installation position thereof. That arrangement of the individual parts relative to each other also requires a comparatively large fitting opening in the tank which, as already indicated above, is often undesirable.
EP 0 922 603 A1 sets forth an arrangement of two fuel reservoirs for being accommodated in a fuel tank, which are flexibly connected together at one side and at the bottom, more specifically by way of flexible bars which in a fitment configuration permit the reservoirs to assume an angled relationship with each other. The reservoir which is to be introduced first into the tank is fitted in a tilted position into the fitting opening of the tank, in such a manner that its upper end is firstly directed transversely with respect to the bottom of the tank. In order to arrange that reservoir in the installation position thereof, the first reservoir has to be turned through 90xc2x0 in the tank when the second or main reservoir is being introduced into the fitting opening of the tank, in which case the main reservoir must be tilted in the fitting opening in the tank. This means that the operation of introducing that arrangement into the tank is extremely complicated and time-consuming. Ultimately, the fact that the reservoir which is to be introduced last into the tank must be tilted upon pivotal movement of the reservoir which is first inserted into the tank means that it is necessary for the internal width of the fitting opening to be selected of a correspondingly large size, which basically is something that is not wanted, as already indicated above.
An object of the present invention is to provide a fuel delivery unit which is so designed that it always affords a sufficiently large delivery volume for a fuel pump while nonetheless being so compact that the fitting opening for same in the fuel tank can still be comparatively small.
Another object of the present invention is to provide a fuel delivery unit which affords enhanced versatility in terms of fitting it into a fuel tank to make the fitting operation easier to implement.
Still another object of the present invention is to provide a fuel delivery unit which while being of a simple structure call afford the possibility of structural re-configuring thereof for greater ease of fitting it into a motor vehicle fuel tank.
In accordance with the principles of the present invention the foregoing and other objects are attained by a fuel delivery unit with an installation holder which provides for bracing the arrangement in relation to the bottom of a tank by suitable means such as compression springs or flexible damping elements or the like and which accommodates at least one first reservoir with a fuel pump disposed therein and a closure cover for a fitting opening in the fuel tank. The fuel delivery unit also includes a second reservoir which in the installation position is disposed beside the first reservoir, the first and second reservoirs communicating with each other. The first and second reservoirs are carried by the installation holder axially displaceably and/or pivotably relative to each other at least in an installation configuration, while retaining the axial orientation thereof. At least one reservoir is arranged in the tank at least in the installation configuration at least partly outside the projected area of the cover closure.
In accordance with the present invention the reference to retaining the axial orientation is intended to mean that the basic orientation of the reservoirs in terms of the longitudinal extent thereof in the fitting configuration or upon being introduced into the tank should correspond to that of the installation position. Such a design configuration for the fuel delivery unit means that it is possible for the individual groups of the delivery unit to be moved relative to each other, that is to say pivoted or axially displaced, from a fitting configuration into an installation configuration and possibly conversely, in such a way that the fuel delivery unit in the fitting configuration takes up less space than in the installation configuration and it call be fitted through a comparatively small fitting opening in the fuel tank. In the installation position of the fuel delivery unit the components thereof can be moved relative to each other into the installation configuration so that the fuel delivery unit can be braced to or secured to the bottom of the tank in its installation configuration which takes up comparatively more space than its fitting configuration.
In accordance with a preferred feature, at least one reservoir and more preferably the first reservoir is guided longitudinally displaceably on the installation holder or on the other reservoir in such a way that the spacing thereof relative to the cover closure is variable for fitting purposes. The xe2x80x98extendibilityxe2x80x99 of the overall arrangement, which is achieved thereby, means that the parts of the fuel delivery unit which are first introduced into the tank can be displaced in the tank into the installation position before the entire assembly is definitively introduced.
In a further preferred feature the second reservoir is arranged within the projected area of the cover closure.
The means for longitudinally slidably guiding a reservoir can comprise at least one and for example preferably two extendible extension portions which are slidably guided and the extension length of which can be such that the reservoir which is first introduced into the fitting opening is displaceable in the tank substantially transversely to the direction of introduction into its installation position, making use of the internal width of the fitting opening in the tank.
In an advantageous configuration of the fuel delivery unit according to the invention the above-mentioned extension portions are guide rails which are provided with end abutments and which are longitudinally slidably and non-rotatably carried on the one hand by sliding guides of the first reservoir and on the other hand by sliding guides of the second reservoir or by sliding guides of the installation holder. That means that the entire arrangement can provide for a telescoping movement thereof, wherein the end abutments on the guide rails ensure on the one hand that they cannot come completely out of the sliding guides, and on the hand they limit the possible extension length. Finally, this arrangement means that it is possible to guarantee that a reservoir is pressed against the bottom of the tank by way of the installation holder and the other reservoir in question.
In a further preferred feature of the invention the guide rails are in the form of I-profile rails and the sliding guides form C-profile grooves which embrace the flanges of the I-profile rails in positively locking relationship therewith.
In a further preferred feature of the invention the first and second reservoirs can be communicated with each other at their bottoms by way of flexible conduits on the basis of the principle of communicating vessels so as to ensure that the reservoirs are each filled to the same filling level. A fuel delivery pump or a fuel delivery assembly is disposed only in one of the reservoirs, in which case the above-described communication also ensures that the reservoirs are emptied at the same time and uniformly with each other.
It would however also be possible to provide a respective fuel delivery assembly in each of the reservoirs. Both of those assemblies can supply fuel to the engine, or one of them could supply fuel to the respective other reservoir.
In accordance with another preferred feature of the invention the communicating conduit for the reservoirs is arranged to extend substantially below same, more specifically in such a way that, when the reservoirs are in the condition of being moved away from each other, that is to say they are in the fitting configuration thereof, the communicating conduit projects scarcely or not at all out of the projected area of the reservoirs. In that way it is possible for the diameter of the fitting opening in the tank to be only immaterially larger than the diameter of the reservoirs, thereby ensuring that the fitting operation can proceed without major problems.
A preferred feature of the invention provides that the position of the connections of the reservoirs to the communicating conduit relative to each other is so selected that, when the tank assumes an inclined position, a discharge flow of fuel from that reservoir which contains the fuel pump is prevented, but a feed flow of fuel to that reservoir from the respective other reservoir is possible.
It is also preferable for the fuel filter to be provided between the cover closure and a reservoir, preferably the second reservoir. The return from the fuel filter, which is by way of a pressure-regulating valve, feeds into the second reservoir. In that way the space between the cover closure and a reservoir is put to optimum use, and the fuel filter or the fuel filter housing and one of the reservoirs are thus arranged in mutual alignment. For example, the pressure-regulating valve which is connected to the fuel filter housing can at least partially project into one of the reservoirs, in the installation configuration of the unit.
Preferably, the fuel filter is accommodated by a filter housing forming a structural unit with the cover closure.
In a preferred feature of the invention the installation holder can be in the form of a telescopic linkage assembly which permits the entire arrangement to be braced against the bottom of a tank, against the force of compression springs provided for that purpose.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of a preferred embodiment thereof.